Evolution in vitro is a powerful tool used to direct the evolution of biocatalysts. To date the experimental systems utilized to select for desired catalysts are necessarily restricted from the direct selection for multiple turnover reactions. This proposal describes a system of evolution in vitro via liposomal encapsulation that is based upon both biological membrane sciences as well as evolution in vitro techniques. Combining elements of these two fields provides an opportunity to select biomolecules directly for multiple turnover reactions. A test of this liposomal encapsulation system will be performed by selecting a pool of hammerhead ribozymes for multiple turnover, RNA cleavage reactions. In addition, the general applicability of this new technique will be explored by evolving not only RNA enzymes but protein catalysts as well. Evolution in vitro via liposomal encapsulation imparts a higher degree of control over selection for exceedingly functional biological catalysts that can potentially be used for gene therapy as well as other forms of bioremediation.